用于在动态数组之间移动结构的 C 方法

Question

我有一个 C 语言的纸牌游戏（我必须在 C 类项目中制作它）。我创建了一种将结构从一个动态数组移动到另一个的方法。不幸的是，该方法起初有效，但后来当我在程序中调用它时，它开始抛出 malloc() 错误。 Deck 是一个结构体，包含一个int size 和一个动态分配的Card *deck，而Card 是一个用于存放单张卡片的结构体。有什么我遗漏的东西，或者必须以其他方式定义吗？

void moveCard(Deck *src, Deck *dest, int n){
    Card *tmpCards = NULL;
    Card tmp = (*src).deck[n];                          // get card to be copied
    int newSize = dest->size + 1;                       //increase dest size by 1
    tmpCards = (Card *) malloc(sizeof(Card) * newSize); // allocate new memory area
    memmove(&(tmpCards[0]), &(dest->deck[0]), sizeof(Card) * (newSize - 1)); 
        // copy all the cards from old memory area to new area
    dest->deck = tmpCards;  // reassign old pointer to new memory area
    dest->size = newSize;   // reevaluate size
    dest->deck[newSize - 1] = tmp; // copy card to end of new area


    tmpCards = NULL; // empty out pointer (no functionality, just for easier reading)
    newSize = src->size; // reevaluate newSize 
    tmpCards = (Card *) malloc(sizeof(Card) * (newSize - 1));
                     // allocate smaller mem area by 1
    memmove(&(tmpCards[0]),&(src->deck[0]), sizeof(Card) * (n));
                     // copy all cards up to the n-th point 
    memmove(&(tmpCards[n]),&(src->deck[n+1]), sizeof(Card) * (newSize - n));
                     // copy all cards from the n+1 -th point

    src->size = newSize -1; // reevaluate size
    src->deck = tmpCards;     // reassign pointer

    // since all input parameters were pointers, no return is necessary
}

编辑：对我不释放内存这一事实的关注的人。原始代码中有 2 个免费命令（free(dest->deck) 和 free(src->deck)）。但只有其中一个有效。另一个出于某种奇怪的原因再次造成了内存损坏，所以我发现它更好，而不是把它们放在这个例子中。

Answer 1

我认为您的内存不足是因为您没有释放任何内存。你只是在分配新的内存。

void moveCard(Deck *src, Deck *dest, int n){
    Card *tmpCards = NULL;
    Card tmp = (*src).deck[n];                          // get card to be copied
    int newSize = dest->size + 1;                       //increase dest size by 1
    tmpCards = (Card *) malloc(sizeof(Card) * newSize); // allocate new memory area
    memmove(&(tmpCards[0]), &(dest->deck[0]), sizeof(Card) * (newSize - 1)); 
        // copy all the cards from old memory area to new area

    // **** CORRECTION ****
    // Free previously allocated memory for dest->deck
    free(dest->deck);

    dest->deck = tmpCards;  // reassign old pointer to new memory area
    dest->size = newSize;   // reevaluate size
    dest->deck[newSize - 1] = tmp; // copy card to end of new area


    tmpCards = NULL; // empty out pointer (no functionality, just for easier reading)
    newSize = src->size; // reevaluate newSize 
    tmpCards = (Card *) malloc(sizeof(Card) * (newSize - 1));
                     // allocate smaller mem area by 1
    memmove(&(tmpCards[0]),&(src->deck[0]), sizeof(Card) * (n));
                     // copy all cards up to the n-th point 
    memmove(&(tmpCards[n]),&(src->deck[n+1]), sizeof(Card) * (newSize - n));
                     // copy all cards from the n+1 -th point

    src->size = newSize -1; // reevaluate size

    // **** CORRECTION ****
    // Free previously allocated memory for src->deck
    free(src->deck);

    src->deck = tmpCards;     // reassign pointer

    // since all input parameters were pointers, no return is necessary
}

PS您应该使用memcpy 而不是memmove。如果源和目标重叠，memmove 是正确的函数。如果源和目标不重叠，memcpy 是正确的函数。